The Rottweiler is good-natured, placid in basic disposition, very devoted, obedient, biddable and eager to work. His appearance is natural and rustic, his behaviour self-assured, steady and fearless. He reacts to his surroundings with great alertness and at the same time even-tempered.

In the American Kennel Club's "Official Standard of the Rottweiler," the Rottweiler's temperament should be:

A calm, confident and courageous dog with a self-assured aloofness that does not lend itself to immediate and indiscriminate friendships. A Rottweiler is self-confident and responds quietly and with a wait-and-see attitude to influences in its environment. It has an inherent desire to protect home and family, and is an intelligent dog of extreme hardness and adaptability with a strong willingness to work, making them especially suited as a companion, guardian and general all-purpose dog.

According to the American Rottweiler Club:

For us, Rottweilers are the best breed in the world, but we firmly believe they are not a dog for everyone. Rottweilers require a calm, stable and firm “pack leader” or they will assume that role for you. Puppies AND adults need socialization, exercise and stimulating mental challenges. With these things, you will have a wonderful companion; without them, your Rottweiler may become destructive and out of control.

Rottweilers are a powerful breed with well-developed genetic herding and guarding instincts. Potentially dangerous behaviour in Rottweilers usually results from irresponsible ownership, abuse, neglect, or lack of socialisation and training. However, the exceptional strength of the Rottweiler is an additional risk factor not to be neglected. It is for this reason that breed experts declare that formal training and extensive socialisation are essential for all Rottweilers. According to the AKC, Rottweilers love their owners and may behave in a clownish manner toward family and friends, but they are also protective of their territory and do not welcome strangers until properly introduced. Obedience training and socialization are required.

One study published in 2008 found that male Rottweilers have higher confidence, sharpness, and defense and play drives than females.

A 2008 study surveying breed club members found that while Rottweilers were average in aggressiveness (bites or bite attempts) towards owners and other dogs, it indicated they tend to be more aggressive than average toward strangers. This aggression appears correlated with watchdog and territorial instincts.

In the Rottweiler Handbook, Joan H. Walker states that "The Rottweiler is very territorial", meaning that the owner will have to regularly work with the dog to control its territorial aggressiveness.